Aqueous coating compositions and their use for the preparation of coatings that are permeable to water vapor

ABSTRACT

The invention relates to coating compositions used to prepare coatings having water vapor permeabilities of at least 2500 g/m 2  per day (DS 2109 TM1 method) containing 
     (A) a polyurethane containing (1) 0.1 to 75 meq/100 g of ionic groups and (2) 11 to 50% by weight of --(CH 2  CH 2  O) n  -- units (wherein n is 2 to 25) incorporated into the main chain prepared from reactive components comprising 
     (I) one or more polyisocyanates, 
     (II) one or more polyols having a number average molecular weight of 350 to 5000, with the proviso that if any such polyol is a sulfonated polyether diol having the formula ##STR1## in which R is hydrogen or an organic group having 1 to 8 carbon atoms, m and n are 1 to 10, p is 0, 1, or 2, and M is ammonium or alkali metal cation, then an additional ethoxy-containing polyether polyol must also be present, and 
     (III) one or more chain lengthening agents having a molecular weight of 32 to 349; and 
     (B) 30 to 80% by weight, based on the sum of components (A) and (B), of an aqueous phase.

This application is a Continuation-In-Part of application Ser. No.08/294,215 filed on Aug. 22, 1994, which is a Continuation-In-Part ofapplication Ser. No. 08/139,385 filed on Oct. 19, 1993, both abandoned.

BACKGROUND OF THE INVENTION

The invention relates to the coating of substrates, in particularflexible substrates such as textile sheets, with agents obtained from(A) polyurethanes containing hydrophilic groups and (B) an aqueousphase. The invention further relates to the use of these agents for thepreparation of coatings which are permeable to water vapor. The term"polyurethanes" as used in this invention includes polyurethane ureas.

Coatings that are highly permeable to water vapor have in the pastrepeatedly been the object of investigations and developments for whichthey are particularly suitable, for example, for the manufacture of highquality leather substitutes or for the production of garments havinghigh wearing comfort.

Because immersion bath and evaporation coagulation, incorporation, andsubsequent washing out of water-soluble salts, as well as perforation bymeans of high energy electron beams, produce micro-channels ormicrocavities in the coating and thereby weaken the coating, it is ofparticular interest to obtain coatings that are permeable to water vaporbut which are free from pores.

Most polyurethanes used for coating compositions are dissolved ordispersed in organic solvents but the trend toward using coatingcompositions containing little or no solvent favors the use of aqueouscoating systems. Polyurethanes that are self-emulsifiable due to thepresence of hydrophilic groups and that can therefore be dispersed inwater without the aid of external emulsifiers are known. See GermanPatentschriften 2,446,440, 2,551,094, 2,651,505, 2,651,506, and2,659,617 and German Offenlegungsschrift 2,816,815 (as well as therespective counterpart U.S. Pat. Nos. 4,108,814, 4,092,286, 4,238,378,4,237,264, 4,293,617, and 4,303,774); compare British Patent 1,510,953(leather primer to enhance adherence of subsequent dressing layers). Anoptimum combination of dispersibility of the polyurethane in water withhigh permeability to water vapor and sufficient water resistance of thecoatings, such as required for coating compositions used for thepreparation of water vapor permeable coatings, has, however, not beenavailable until now.

It has now surprisingly been found that coatings that are highlypermeable to water vapor and have very little tendency to swell in watercan be prepared by using, as coating compositions, systems containing(A) polyurethanes that contain ionic groups and polyethylene oxide unitshaving defined quantity and sequence length and (B) an aqueous phase.

SUMMARY OF THE INVENTION

The present invention thus relates to coating compositions used for thepreparation of coatings having a water vapor permeability of at least2500 g/m² per day (preferably at least 3000 g/m² per day, mostpreferably from 3600 to 25,000 g/m² per day) using the DS 2109 TM1method comprising

(A) a polyurethane containing (1) from 0.1 to 75 meq (preferably from0.5 to 40 meq) per 100 g of polyurethane (A) of ionic groups preferablyselected from the group consisting of (a) alkali metal and ammoniumsalts of carboxylate groups, (b) alkali metal and ammonium salts ofsulfonate groups, (c) ammonium groups, and (d) mixtures thereof, and (2)6 to 50% by weight (preferably 10 to 40% by weight and more preferablyfrom 10 to 35% by weight), based on polyurethane (A), of polyethyleneoxide --(CH₂ CH₂ O)_(n) -- units having a sequence length n of from 2 to50 (preferably from 2 to 25 and more preferably from 3 to 12)incorporated into the main chain, wherein said polyurethane (A) isprepared from reactive components comprising

(I) one or more polyisocyanates,

(II) one or more polyols (preferably diols) having an average molecularweight of from 350 to 5000 (preferably from 800 to 2500), with theproviso that if any such polyol is a sulfonated polyether diol havingthe formula ##STR2## wherein R denotes hydrogen or an organic grouphaving 1 to 8 carbon atoms, m and n independently represent the numbers1 to 10, p represents 0, 1, or 2, and M denotes ammonium or the cationof an alkali metal, then at least one additional polyether polyolcontaining ethoxy groups must also be present, preferably in quantitiessuch that at least 25% (more preferably at least 50%) of the ethoxygroups incorporated into the main chain of polyurethane (A) are derivedfrom said additional polyol, and

(III) one or more chain lengthening agents having a molecular weight offrom 32 to 349; and

(B) from 30 to 80% by weight, based on the sum of components (A) and(B), of an aqueous phase.

DETAILED DESCRIPTION OF THE INVENTION

The term "incorporated into the main chain" as used in the context ofthis invention means that the polyethylene oxide units do not form theend of a chain but are attached at both ends to radicals each of whichcontains at least one urethane or urea group. "Incorporated into themain chain" is thus contrasted to the conventional concept of"terminally positioned" or "laterally positioned". Cf., European PatentApplication 347 (page 9).

The effect achievable with the coating compositions according to theinvention is very surprising because polyurethanes which contain eitherthe ionic groups alone or the polyethylene oxide units of the typedefined in the claims alone do not, for practical purposes, have anypermeability to water vapor.

The polyurethanes described in German Patentschriften 2,551,094,2,651,505, 2,651,506, and 2,659,617 and in German Offenlegungsschrift2,816,815 contain polyethylene oxide units in terminal positions and/orlateral positions and thus do not satisfy the requirements according tothe present invention.

In the polyurethanes described in German Patentschrift 2,446,440(counterpart of U.S. Pat. No. 4,108,814), sulfonated diol units that mayalso contain alkylene oxide units of unspecified sequence length areincorporated into the main polymer chain in such a quantity that thepolyurethanes have a sulfonate group content of 0.1 to 6% by weight.However, only propoxylated or ether group-free sulfonated diols are usedin the examples. Hydroxyl compounds other than sulfonated diols aredescribed as suitable for incorporation into such polyurethanes, butonly polyester diols are used in the examples. Polyether polyols freefrom sulfonate groups are not used. German Patentschrift 2,446,440,therefore, does not suggest that improved coating compositions would beobtained by incorporating both ionic groups and polyethylene oxide unitshaving sequence lengths of from 2 to 50 into a polyurethane in thespecified quantity of 6 to 50% by weight. In addition, the German patentdoes not mention water vapor permeable coatings and thus could notsuggest using polyurethane dispersions for the preparation of watervapor permeable coatings.

For the preparation of coatings that are permeable to water vapor, itwas necessary to overcome a preconception insofar as one skilled in theart would regard it as highly probable that coatings based onpolyurethanes that contain not only ionic groups but in addition otherhydrophilic groups (such as polyethylene oxide units) would not providesufficient wet resistance. Even with hindsight it still appearsextremely surprising that dispersibility of the polyurethanes in waterand high permeability to water vapor could be combined with good wetstrength of the resulting coatings.

The polyurethanes (A) may be prepared in known manner, eithersolvent-free or, preferably, in an organic solvent.

Polyurethanes (A) are prepared from polyisocyanates of the formulaQ(NCO)₂ in which Q stands for an aliphatic hydrocarbon group having 4 to12 carbon atoms, a cycloaliphatic hydrocarbon group having 6 to 25carbon atoms, an aromatic hydrocarbon group having 6 to 15 carbon atoms,or an araliphatic hydrocarbon group having 7 to 15 carbon atoms.Examples of such preferred diisocyanates include tetramethylenediisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate,1,4-diisocyanatocyclohexane,3-isocyanatomethyl-3,3,5-trimethylcyclohexylisocyanate (isophoronediisocyanate), 4,4'-diisocyanatodicyclohexylmethane,4,4'-diisocyanato-3,3'-dimethyldicyclohexylmethane,4,4'-diisocyanatodicyclohexylpropane-(2,2), 1,4-diisocyanatobenzene,2,4- or 2,6-diisocyanatotoluene or mixtures of these isomers, 4,4'-,2,4'- or 2,2'-diisocyanatodiphenylmethane or mixtures of these isomers,4,4'-diisocyanatodiphenylpropane-(2,2), p-xylylene diisocyanate andα,α,α',α'-tetramethyl-m- or -p-xylylene diisocyanate, and mixtures ofthese compounds.

The higher functional polyisocyanates known from polyurethane chemistryand known modified polyisocyanates, such as polyisocyanates containingcarbodiimide groups, allophanate groups, isocyanurate groups, urethanegroups, and/or biuret groups, may, of course, also be used as all orpart of the polyisocyanate component.

The reactants used for the polyisocyanates are mainly polyhydroxylcompounds containing from 2 to 8 (preferably 2 or 3) hydroxyl groups permolecule and having a molecular weight (average) of up to 5000(preferably up to 2500). Both low molecular weight polyhydroxylcompounds having molecular weights of from 32 to 349 and relatively highmolecular weight polyhydroxyl compounds having average molecular weightsof at least 350 (preferably at least 1000), such as those described indetail in the above-mentioned publications, may be used.

Relatively high molecular weight polyhydroxyl compounds include thehydroxypolyesters, hydroxypolyethers, hydroxypolythioethers,hydroxypolyacetals, hydroxypolycarbonates, and/or hydroxypolyesteramides known in polyurethane chemistry, preferably those having averagemolecular weights of from 600 to 4000 and most preferably those withaverage molecular weights of from 800 to 2500. Polycarbonate polyols,polyether polyols, and polyester polyols, as well as polyether carbonatepolyols, polyether ester polyols, and polyester carbonate polyols, andmixtures thereof are particularly preferred.

Components suitable for use in the synthesis of the polyurethanes (A)for introducing polyethylene oxide units include homopolyethyleneglycols and ethylene oxide copolyethers (preferably ethyleneoxide/propylene oxide mixed ethers) containing hydroxyl end groups andhaving a block or random distribution, provided that the ethylene oxidesequences satisfy the requirements according to the invention. Amongthese, polyether carbonates and polyether esters based on theabove-mentioned homopolyethylene glycols, ethylene oxide copolyethers ormixtures thereof with other polycarbonate-forming or polyester-formingpolyhydroxyl compounds are preferred. If copolyethers or polyethercarbonates or polyether esters based on such copolyethers are used ascomponents for introducing the polyethylene oxide units into thepolyurethane (A) or its precursors, only those units which have thesequence lengths as claimed herein count as polyethylene oxide sequenceswithin the meaning of the invention, while those polyethylene oxidesequences which have a sequence length above or below the limits claimedare not included.

The optimum quantity of polyethylene oxide units in polyurethane (A)depends to some extent on the sequence length and follows the rule thatif the sequence length is short the quantity may be slightly greater andif the sequence length is great the quantity may be slightly smaller.Thus with a sequence length of 2, the quantity of these polyethyleneoxide units in polyurethane (A) may be up to 50% by weight, whereas ifthe sequence length is above 20, it is advisable to limit the quantityof these polyethylene oxide units in polyurethane (A) to 20% by weight.

Monofunctional polyethylene oxide alcohols (i.e., ethoxylated monohydricalcohols or ethoxylated phenols) may be incorporated into polyurethane(A) in quantities of from 0.2 to 5% by weight, based on polyurethane(A), for assisting the dispersing action. If such monofunctionalpolyethylene oxide alcohols are incorporated into polyurethane (A), theproportion of ionic groups may be reduced but these monofunctional unitsmake hardly any contribution to the permeability of the coatings towater vapor. The proportion of such monofunctional polyethylene oxideunits in polyurethane (A), based on the total quantity of polyethyleneoxide units incorporated, should not exceed 30% by weight and ispreferably not more than 20% by weight (more preferably not more than10% by weight). Best results are obtained when no monofunctionalpolyethylene oxide units are incorporated.

Starting components which supply the polyethylene oxide units forpolyurethane (A) thus include mainly ethylene oxide polyethers andethylene oxide/propylene oxide mixed polyethers having 2 or 3 hydroxylgroups. Pure ethylene oxide polyethers are particularly preferred. Evenwhen using mixed polyethers, it is generally preferred to use polyetherscontaining an amount by weight of ethylene oxide units at least equal tothe amount of propylene oxide units.

The term "average molecular weights" in the context of this inventiondenotes molecular weights determined as number average molecularweights.

Compounds that are used in addition to the components supplying thepolyethylene oxide units defined in the claims may be selected from theisocyanate-reactive compounds conventionally used in polyurethanechemistry.

Polyhydroxyl components that are suitable as starting materials forpolyurethanes but which do not contain the polyethylene oxide unitsaccording to the invention are described below.

Suitable hydroxyl group-containing polycarbonates are obtainable by thereaction of carbonic acid derivatives such as diphenyl carbonate orphosgene with diols. Suitable diols for this purpose include ethyleneglycol, 1,2- and 1,3-propanediol, 1,4- and 1,3-butanediol,1,6-hexanediol, 1,8-octanediol, neopentyl glycol,1,4-bis(hydroxymethyl)cyclohexane, 2-methyl-1,3-propanediol,2,2,4-trimethyl-1,3-pentanediol, dipropylene glycol, polypropyleneglycol, dibutylene glycol, polybutylene glycol, bisphenol A, andtetrabromobisphenol A. The diol component preferably contains from 40 to100% by weight of hexanediol, preferably 1,6-hexanediol, and/orhexanediol derivatives, preferably those containing ether or estergroups in addition to OH end groups, for example, products obtained bythe reaction of 1 mol of hexanediol with at least 1 mol (preferably 1 to2 mol) of caprolactone according to the method of German Auslegeschrift1,770,245 or by the autoetherification of hexanediol to form di- ortrihexylene glycol. The preparation of such derivatives has beendisclosed, for example, in German Auslegeschrift 1,570,540. Thepolyether-polycarbonate diols described in German Offenlegungsschrift3,717,060 are also very suitable.

The hydroxyl polycarbonates should be mainly linear but may, if desired,be slightly branched by the incorporation of polyfunctional components,in particular low molecular weight polyols. Glycerol,trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol,trimethylolpropane, pentaerythritol, quinitol, mannitol and sorbitol,methyl glycoside, and 1,4,3,6-dianhydrohexitols, for example, aresuitable for this purpose.

Suitable polyether polyols other than those described above include thepolyethers known in polyurethane chemistry, for example, the addition ormixed addition compounds of tetrahydrofuran, styrene oxide, propyleneoxide, the butylene oxides, or epichlorohydrin obtained by reaction withdivalent starter molecules such as water, the above-mentioned diols, oramines containing two NH bonds, in particular the addition or mixedaddition compounds of propylene oxide.

Examples of suitable polyester polyols include the reaction products ofpolyvalent (preferably divalent) alcohols, optionally together withtrivalent alcohols, with polybasic (preferably dibasic) carboxylicacids. Instead of using free polycarboxylic acids, the correspondingpolycarboxylic acid anhydrides or corresponding polycarboxylic acidesters of lower alcohols or mixtures thereof may be used for thepreparation of the polyesters. The polycarboxylic acids may bealiphatic, cycloaliphatic, aromatic, and/or heterocyclic and may besubstituted (e.g., by halogen atoms) and/or unsaturated. Examples ofsuitable polycarboxylic acids and derivatives thereof include succinicacid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalicacid, isophthalic acid, trimellitic acid, phthalic acid anhydride,tetrahydrophthalic acid anhydride, hexahydrophthalic acid anhydride,tetrachlorophthalic acid anhydride, endomethylene tetrahydrophthalicacid anhydride, glutaric acid anhydride, maleic acid, maleic acidanhydride, fumaric acid, dimeric and trimeric fatty acids such as oleicacid optionally mixed with monomeric fatty acids, terephthalic aciddimethyl ester and terephthalic acid bis-glycol ester. Examples ofsuitable polyhydric alcohols include ethylene glycol, 1,2- and1,3-propanediol, 1,4-and 2,3-butanediol, 1,6-hexanediol, 1,8-octanediol,neopentyl glycol, cyclohexanedimethanol,1,4-bis(hydroxymethyl)cyclohexane, 2-methyl-1,3-propanediol, glycerol,trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol,trimethylolethane, pentaerythritol, quinitol, mannitol and sorbitol,methylglycoside, diethylene glycol, triethylene glycol, tetraethyleneglycol, dipropylene glycol, dibutylene glycol, and polybutylene glycols.Polyester polyols are generally not used alone in component (II) unlessthey contain polyethylene oxide --(CH₂ CH₂ O)_(n) -- units having asequence length n of from 2 to 50 (as described above) or are used incombination with other types of polyols.

Mixtures of the above mentioned polyether polyols with polycarbonatepolyols and/or polyester polyols having average molecular weights offrom 1000 to 3000 and obtained from adipic acid, 1,6-hexanediol, andneopentyl glycol are particularly preferred.

Further starting components for the preparation of polyurethanes (A) arein particular chain lengthening agents having molecular weights of from32 to 299 and containing 1,4-hydroxyl and/or amino groups.

Low molecular weight polyhydroxyl compounds ("chain lengthening agents")include a wide variety of diols such as, for example:

a) Alkane diols such as ethylene glycol, 1,2- and 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, dimethyl-1,3-propanediol, and1,6-hexanediol;

b) Ether diols such as diethylene glycol, triethylene glycol, orhydroquinone dihydroxyethyl ether;

c) Ester diols corresponding to the following general formulas:

    HO--(CH.sub.2).sub.x --CO--O--(CH.sub.2).sub.y --OH

and

    HO--(CH.sub.2).sub.x --O--CO--R--CO--O--(CH.sub.2).sub.x --OH

wherein

R denotes an alkylene or arylene group having 1 to 10 (preferably 2 to6) carbon atoms,

x is from 2 to 6, and

y is from 3 to 5,

for example, δ-hydroxybutyl-ε-hydroxycaproic acid ester,ω-hydroxyhexyl-γ-hydroxybutyric acid ester, adipic acid β-hydroxyethylester, and terephthalic acid bis(β-hydroxyethyl) ester.

Polyamines may also be used as chain lengthening agents and arepreferably aliphatic or cycloaliphatic diamines, although trifunctionalor higher functional polyamines may also be included for producing aparticular degree of branching. Examples of suitable aliphaticpolyamines include ethylenediamine, 1,2- and 1,3-propylenediamine,1,4-tetramethylenediamine, 1,6-hexamethylenediamine, the isomericmixture of 2,2,4- and 2,4,4-trimethylhexamethylenediamine,2-methyl-pentamethylenediamine, and bis(β-aminoethyl)amine(diethylenetriamine).

Suitable cycloaliphatic polyamines include ##STR3##

Araliphatic polyamines such as 1,3- and 1,4-xylylenediamine orα,α,α',α'-tetramethyl-1,3- and -1,4-xylylenediamine may also be used aschain lengthening agents for the preparation of polyurethanes (A).

Hydrazine, hydrazine hydrate, and substituted hydrazines are also to beregarded as diamines for the purpose of this invention. Examples includemethyl hydrazine, N,N'-dimethyl hydrazine and their homologs, and aciddihydrazides, such as carbodihydrazide, oxalic acid dihydrazide, thedihydrazides of malonic acid, succinic acid, glutaric acid, adipic acid,β-methyladipic acid, sebacic acid, hydracrylic acid and terephthalicacid, semicarbazido-alkylene hydrazides such as β-semicarbazidopropionicacid hydrazide (German Offenlegungsschrift 1,770,591), semicarbazidoalkylene carbazic esters such as 2-semicarbazidoethyl carbazic ester(German Offenlegungsschrift 1,918,504), or aminosemicarbazide compoundssuch as β-aminomethylsemicarbazido carbonate (German Offenlegungsschrift1,902,931).

Ionic groups for the polyurethanes (A) include alkali metal and ammoniumcarboxylate and sulfonate groups and ammonium groups. Suitablecomponents for introducing these ionic groups into the polyurethanes (A)include dihydroxycarboxylic acids, diaminocarboxylic acids,dihydroxysulfonic acids, and diaminoalkylsulfonic acids and their salts,for example, dimethylolpropionic acid, ethylenediamino-β-ethylsulfonicacid, ethylenediamino-propyl- or -butyl-sulfonic acid, 1,2- or1,3-propylenediamine-β-ethylsulfonic acid, lysine, 3,5-diaminobenzoicacid, and their alkali metal and/or ammonium salts, as well as theadduct of sodium bisulfite with 2-butene-1,4-diol.

The preferred components used for introducing the ionic groups intopolyurethanes (A) include, in particular, the aliphatic diols containingsulfonate groups according to German Offenlegungsschrift 2,446,440 thatcorrespond to the following formula ##STR4## wherein

R denotes hydrogen or an organic group having 1 to 8 carbon atoms,

m and n independently represent the numbers 1 to 10, and

M denotes ammonium or the cation of an alkali metal.

It is also possible, although generally less preferred, to introduce theionic groups into polyurethanes (A) using other aliphatic diolscontaining sulfonate groups that correspond to the following formula##STR5## wherein R, M, m, and n are defined as above and p represents 1or 2.

Examples of cationic or potentially cationic starting components includediols having tertiary amino groups, such as N-methyl-diethanolamine andits protonation or alkylation products.

The components used for introducing the ionic groups into polyurethanes(A) may in general be cationic and/or anionic hydrophilic difunctionalstarting components of the type described for the preparation of aqueouspolyurethane dispersions, such as, for example, dihydroxyl compounds,diamines, or diisocyanates containing ionic or potentially ionic groups.

The aqueous phase (B) consists for the most part of water but may alsocontain organic auxiliary solvents. Preferred organic auxiliary solventsinclude, for example, amides such as N,N-dimethylformamide,N,N-dimethylacetamide, and N-methylpyrrolidone; ketones such as methylethyl ketone, diacetone alcohol, and cyclohexanone; ethers such asethylene glycol monomethyl-, monoethyl-, and monobutyl ethers and thecorresponding ethers of diethylene glycol, and propylene glycolmonomethyl- and monobutyl ether; and esters such as propylene glycoldiacetate and dipropylene glycol methyl ether acetate. The quantity oforganic auxiliary solvents is preferably up to 20% by weight (preferablyup to 10% by weight), based on the total amount of aqueous phase (B).

Polyurethane (A) which is obtained as a solvent-free melt or in the formof a solution after its preparation may then be converted into anaqueous dispersion by mixing with water and optionally thereafterdistilling off any auxiliary solvent.

Polyurethanes (A) may in principle be converted into aqueous dispersionsby any known process, for example, by dispersion without the aid ofsolubilizing agents, for example, by mixing the solvent-freepolyurethane with water in apparatus capable of producing high shearinggradients, by using very small quantities of organic solvents forplasticizing the polyurethanes in the same apparatus, or by usingnon-mechanical dispersing agents such as extremely high frequency soundwaves. On the other hand, simple mixing apparatus, such as stirrervessels or so-called throughflow mixers, may be used since polyurethane(A) is self-dispersible.

The dispersions may be mixed with other anionic or non-ionicdispersions, for example, with polyvinyl acetate or with polyethylene,polystyrene, polybutadiene, polyvinyl chloride, polyacrylate, orcopolymer dispersions. Known emulsifiers that are not chemically fixed,preferably ionic emulsifiers of this type, may also be added but are, ofcourse, not necessary.

Fillers, plasticizers, pigments, carbon black and silica sols, anddispersions of aluminum, clay, or asbestos may also be incorporated inthe dispersion.

Certain properties of the coatings prepared according to the invention,such as the handle or the surface smoothness, may be modified by meansof oligomeric compounds with molecular weights of from 300 to 6000(preferably from 500 to 1500) containing polysiloxane segments andhaving at least two isocyanate reactive groups. Difunctionalpolysiloxanes containing organofunctional end groups are preferablyused. Such compounds have structural units of the formula --O--Si(R)₂ --wherein R represents a C₁ -C₄ alkyl group or a phenyl group (preferablya methyl group).

The aqueous coating compositions according to the invention are stableand suitable for storage and transport and may be worked up at any latertime. The properties of coatings obtained can be varied according to theselected chemical composition and the urethane group content. Thus,soft, sticky layers and thermoplastic or rubbery elastic products withvarious degrees of hardness up to glass-hard duroplasts may be obtained.The hydrophilic character of the products may also vary within certainlimits. The elastic products may be thermoplastically processed atelevated temperatures, for example, at from 100° to 180° C., providedthey are not chemically cross-linked.

The coating compositions according to the invention are suitable forcoating or dressing and impregnating woven and non-woven textiles,leather, paper, hard fibers, straw, and paper-type materials. For thispurpose, the dispersions or pastes are preferably applied to a poroussupport which subsequently remains bonded to the finished product, forexample, woven or non-woven textiles or fiber mats, felts or non-wovenwebs or paper webs, foam sheets, or split leather, which bring aboutinstant solidification of the coating due to the suction effect of suchsubstrates. The resultant product is subsequently dried at elevatedtemperature and optionally pressed. Drying may also be carried out onsmooth, porous, or non-porous materials, such as metal, glass, paper,cardboard, ceramic materials, steel sheeting, silicone rubber, oraluminum foils. The finished sheet structure is subsequently lifted offand used as such or applied to a substrate by the reversal processentailing gluing, flame backing, or calendering. Application by thereversal process may be carried out at any time.

The coating composition may be applied to the substrate by direct spreadcoating using coating knives, rollers, or wire coaters. It is customaryto apply several coats in succession, preferably in two coats, so thatthe total thickness of the coating composed of undercoat and top coat(s)amounts to 10 to 100 μm (preferably 20 to 60 μm).

The undercoat may also be a paste which dries to form a microporouslayer, as described in German Offenlegungsschrift 2,020,153.

The top coat that is subsequently applied protects the entirecombination of layers against mechanical stress and abrasion.

Application of the coating combination composed of undercoat and topcoat may also be carried out by the so-called reversal process, in whichthe top coat is first applied to a separating support and dried, and,after application of a second undercoat or bonding coat, the textilesubstrate is lightly pressed into the still moist layer. After drying, afirmly bonded combination of coating and substrate is obtained. Thisbonded combination is detached from the separating support and issubstantially similar in its structure to the direct coating productdescribed above.

The coating compositions according to the invention give rise tocoatings in which the permeability to water vapor has surprisinglylittle dependence upon the thickness of the layer over a wide range oflayer thicknesses. The coatings do not swell noticeably in water.

The coatings, which are exceptionally permeable to water vapor andabsolutely resistant to drops, may also be prepared from aqueousdispersions containing pigments and/or dyes. Hydrophobicizing agentssuch as fluorocarbon resins, waxes, and oils may also be added, providedthey do not unduly impair the permeability to water vapor. Crosslinkingadditives that undergo a reaction on their own or with polyurethane (A)only in the finished coating, generally by the action of heat, may alsobe used. Examples of such compounds include (partially) etherifiedmelamine formaldehyde resins (e.g., hexamethylol melamine) andpolyisocyanates that are optionally blocked and have 3 or moreisocyanate groups (e.g., based on tris(isocyanatohexyl)isocyanurate andtris(isocyanatohexyl)biuret).

The invention further relates to the use of the coating compositionsaccording to the invention for the preparation of water vapor permeablecoatings, in particular, on flexible substrates, such as textiles,leather, paper, and the like.

The following examples further illustrate details for the preparationand use of the compositions of this invention. The invention, which isset forth in the foregoing disclosure, is not to be limited either inspirit or scope by these examples. Those skilled in the art will readilyunderstand that known variations of the conditions and processes of thefollowing preparative procedures can be used to prepare thesecompositions. Unless otherwise noted, all temperatures are degreesCelsius and all parts and percentages are parts by weight andpercentages by weight, respectively.

EXAMPLES

Starting materials used in the Examples:

    ______________________________________                                        Diol I:   Polycarbonate of 1,6-hexanediol and tetraethylene                             glycol (molar ratio 1:1), OH number 56, molecular                             weight 2000, ethylene oxide ("EOX") content 49%                     Diol II:  Polycarbonate of 1,6-hexanediol and tetraethylene                             glycol (molar ratio 2:5), OH number 82, molecular                             weight 1370, EOX content 65%                                        EOX polyether                                                                           Monofuctional polyethylene glycol, OH weight 2250                   III:                                                                          Diol sulfonate IV:                                                                      Product of addition of NaHSO.sub.3 to propoxylated                            butene-1,4-diol, OH number approximately 260,                                 molecular weight 425                                                Diaminosulfonate                                                                        H.sub.2 N--CH.sub.2 CH.sub.2 --NH--CH.sub.2 CH.sub.2 --SO.sub.3               Na                                                                  V:                                                                            ______________________________________                                    

Methods of measurement

The permeability to water vapor ("WVP") was determined by the generalmethod of DS 2109 TM1 of British Textile Technology Group, Manchester,England. A double thickness of capillary matting was saturated withdistilled water and placed in a chamber having a constant temperature of20° C. (±1° C.) and a relative humidity of about 65%. About 15 g of drysilica gel in the form of beads having a diameter of about 3 to 5 mmwere placed in a plastic cup having an internal diameter at the openingof 61 mm, and the cup and its content were accurately weighed (W₁). Testfilms, each of which had a thickness corresponding to about 50 to about75 g/m² (generally 50 to 60 g/m²), were attached firmly over the openingof the plastic cup with a clamping ring and inverted onto thewater-soaked capillary matting, which provides a relative humidity atthe film surface of 100%. After an accurately timed interval of aboutone hour, the cup was removed from the wet capillary matting, theclamping ring and test film were removed from the cup (with care beingtaken to assure that no silica gel beads adhered to the film or wereotherwise lost from the cup), and the cup and its content were againaccurately weighed (W₂). The water vapor permeability in g/m² per daywas calculated from the experimentally determined values W₁ and W₂ (eachin grams) using the formula WVP= (W₂ -W₁)×24!/(a×t), where t is the timein hours between successive weighings and a is the area in m² of theexposed test film (calculated using the formula a=πd² /4, where d is theinternal diameter of the opening in the cup). For the test cups used inthe examples, the formula reduced to WVP=(W₂ -W₁)×8216. The values forwater vapor permeability were relatively insensitive to film thicknesswithin the range of test thicknesses used in the following examples.

The water resistance ("WR"), or resistance to penetration by liquidwater, was determined according to DIN 53,886.

The resistance to drops was determined by subjecting the upper surfaceof the coating to the action of water drops (1 minute). If no pustularchanges occur on the surface, the coating is described as "absolutelydrop resistant".

Example 1

Preparation of an aromatic polyurethane dispersion for water-vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        247.2 g           diol I                                                      15.2 g            EOX polyether III                                           18.0 g            diol sulfonate IV                                           200.0 g           acetone                                                     84.6 g            4,4'-diphenylmethane diisocyanate                           17.0 g            hexane-1,6-diisocyanate                                     18.0 g            acetone azine                                               600.0 g           deionized water                                             ______________________________________                                    

387 g of solid substance contained 10.9 meq of SO₃ Na/100 g and 31.3% byweight of EOX in the main chain.

Method:

The acetone and mixture of the two diisocyanates were stirred into themixture of components I, III, and IV that had been dehydrated at 120°C., and the mixture was left to react under reflux until the isocyanatevalue was constant. After the temperature dropped to 40° C., the acetoneazine was stirred into the isocyanate prepolymer solution. The water wasthen introduced with vigorous stirring, the resulting dispersion wasstirred for a further 2 hours, and the acetone was distilled off.

A film weighing 68 g/m² was prepared to determine the permeability towater vapor (WVP). For this purpose, 100 g of the dispersion wereadjusted to a suitable viscosity for spread coating using 1% of apolyacrylic acid thickener after adjustment of the pH to 8 withconcentrated ammonia. The water vapor permeability was 15,700 g/m² d.

A film weighing 56 g/m² prepared for comparison from a polyurethanedispersion that had been prepared from a formulation containing apolycarbonate of 1,6-hexanediol with molecular weight 2000 instead ofdiol I but which otherwise had the same composition had a permeabilityto water vapor of only 800 g/m² d. The solid substance contained 10.9meq SO₃ Na/100 g and 0% EOX in the main chain.

Example 2

Preparation of an aliphatic polyurethane dispersion for water-vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        129.7 g                                                                              polycarbonate from 1,6-hexanediol, OH number 56,                              molecular weight 2000                                                  114.0 g                                                                              diol I                                                                 82.6 g dihydroxypolypropylene glycol, OH number 56, molecular                        weight 2000                                                            5.0 g  dimethylolpropionic acid                                               59.5 g hexane 1,6-diisocyanate                                                2.2 g  ethylenediamine                                                        1.4 g  hydrazine hydrate                                                      5.6 g  diaminosulfonate V                                                     700.0 g                                                                              acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g of solid substance contained 7.4 meq SO₃ Na/100 g and 14% byweight EOX in the main chain.

Method:

Polycarbonate, diol 1, and dihydroxypolypropylene glycol were dehydratedunder vacuum at 105° C. for 1 hour. Dimethylolpropionic acid was addedat 100° C. and hexanediisocyanate was added at 80° C. After 3 hours at95° C., the resultant prepolymer was dissolved in acetone. The mixtureof chain lengthening agents comprising ethylenediamine, hydrazinehydrate, and diaminosulfonate V dissolved in 120 g of water was addeddropwise at 50° C. The remaining quantity (480 g) of water was thenstirred in. After continuous stirring for 21/2 hours at 40° C., theacetone was removed by distillation. A stable 40% dispersion wasobtained.

To determine the permeability to water vapor, a film weighing 53 g/m²was prepared after thickening as in Example 1. The water vaporpermeability was 9500 g/m² d.

A comparison film prepared from a polyurethane dispersion which insteadof containing diol I contained a larger quantity, corresponding to themolar quantity, of a polycarbonate of 1,6-hexanediol having a molecularweight of 2000 but which otherwise had the same composition and had apermeability to water vapor of only 900 g/m² d in a film having athickness corresponding to 58 g/m². The solid substance contained 7.4meq SO₃ Na/100 g and 0% EOX in the main chain.

Transfer coating:

The dispersion described in Example 1 together with a polyacrylic acidthickener was applied to a commercial separating paper (Transcote® VEMCIS of S. D. Warren Company) by means of a roller applicator withbuilt-in coating knife so that a film of 25 g/m² was obtained afterdrying at 80° to 150° C.

    ______________________________________                                        Spread coating paste:                                                         ______________________________________                                        100 parts                                                                             40% polyurethane dispersion from Example 1                            1 part  polyacrylic acid thickener                                            5 parts aqueous pigment preparation adjusted to pH 8 with                             ammonia                                                               ______________________________________                                    

A spread coating paste prepared analogously from the polyurethanedispersion of Example 2 (without pigment preparation) was applied asbonding layer to the dried film. After lamination of a cotton fabricweighing about 140 g/m² and drying of the whole arrangement of layers at80° to 140° C., the water-vapor permeable article obtained had a totalweight of 200 g/m² and the coating composed of top coat and bonding coatweighed 60 g/m².

The soft article, which has a pleasant handle, has a water vaporpermeability of 6600 g/m² d and a water resistance of 2000 mm.

A transfer article of analogous structure prepared from the comparisondispersions described in Examples 1 and 2 without diol I has a watervapor permeability of 750 g/m² d in a coating weighing 60 g/m².

Example 3

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        245.5 g                                                                              diol I                                                                 75.5 g dihydroxypolypropylene glycol, OH number 56, molecular                        weight 2000                                                            12.7 g EOX polyether III                                                      3.1 g  neopentyl glycol                                                       54.0 g hexane-1,6-diisocyanate                                                2.3 g  ethylenediamine                                                        1.4 g  hydrazine hydrate                                                      4.7 g  diaminosulfonate V                                                     700.0 g                                                                              acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g solid substance contained 6.2 meq SO₃ Na/100 g and 30.0% by weightEOX in the main chain.

Method:

A 40% dispersion was prepared analogously to Example 2. To determine thepermeability to water vapor, the dispersion was thickened as in Example1 and a film weighing 57 g/m² was produced. The water vapor permeabilitywas 3600 g/m² d.

A comparison film produced from a polyurethane dispersion which insteadof containing diol I contained a polycarbonate of 1,6-hexanediol ofmolecular weight 2000 but was otherwise identical in composition had awater vapor permeability of only 750 g/m² d when the film thickness was59 g/m².

Transfer coating:

A spread coating paste prepared from the dispersion of Example 3 wasapplied as bonding layer to the top coat described in Example 2 using amethod analogous to that described in Example 2, and the layers werelaminated at 140° C. with the cotton fabric also described in Example 2.The coating composition composed of top coat and bonding coat weighed 60g/m². The water vapor permeability of the article was 6300 g/m² d and a2000 mm water resistance.

Example 4

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        131.4 g                                                                              polycarbonate of 1,6-hexanediol, OH number 56, molecular                      weight 2000                                                            116.8 g                                                                              diol I                                                                 19.7 g EOX polyether III                                                      6.2 g  dimethylolpropionic acid                                               10.5 g 1,4-butanediol                                                         44.2 g hexane-1,6-diisocyanate                                                58.3 g isophorone diisocyanate                                                3.5 g  ethylenediamine                                                        2.2 g  hydrazine hydrate                                                      7.2 g  diaminosulfonate V                                                     700.0 g                                                                              acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g solid substance contained 9.5 meq SO₃ Na and 14.3% by EOX in themain chain.

Method:

A 40% polyurethane dispersion was prepared from these componentsanalogously to Example 2 by the acetone process.

To determine the permeability to water vapor, a film weighing 52 g/m²was prepared after thickening of the dispersion with 3.0 g of a 30%solution of poly-N-vinylpyrrolidone. The water vapor permeability was11,300 g/m² d.

A comparison film from a polyurethane dispersion analogous to that ofExample 4 in which diol I had been replaced by the equimolar quantity ofhexanediol polycarbonate had a water vapor permeability of 1500 g/m² din a film weighing 48 g/m². The solid substance contained 9.5 meq SO₃ Naand 0% EOX in the main chain.

Transfer coating:

The polyurethane dispersion which had been thickened withpoly-N-vinylpyrrolidone as described above was used for producing a topcoat as in Example 2 after it had been pigmented. The spread coatingpaste described in Example 3 was used as bonding coat. The textilesubstrate used was a mixed fabric of cotton/polyester weighing 100 g/m².The coating composed of top coat and bonding coat weighed 53 g/m². Thewater vapor permeability was 6900 g/m² d. When the bonding coat pastewas used as a so-called beaten foam dispersion, unit weight 500 g/l, thewater vapor permeability was 7500 g/m² d when the total layer weighed 55g/m² and the water resistance was 2000 mm.

When the comparison dispersion mentioned in Example 4 was used as topcoat and the comparison dispersion mentioned in Example 3 was used asbonding coat, the water vapor permeability values were 900 g/m² d(compact) and 1150 g/m² d (foamed).

Example 5

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        74.3 g 1,6-hexanediol polyadipate, OH number 133, molecular                          weight 840                                                             132.2 g                                                                              diol II                                                                27.3 g diol sulfonate IV                                                      6.5 g  trimethylolpropane                                                     33.8 g N-methylpyrrolidone                                                    118.0 g                                                                              dicyclohexylmethane-4,4'-diisocyanate                                  21.5 g hexane-1,6-diisocyanate                                                20.2 g acetone azine                                                          545.0 g                                                                              deionized water                                                        ______________________________________                                    

386 g of solid substance contained 16.7 meq SO₃ Na/100 g and 22.3% byweight EOX in the main chain.

Method:

Trimethylolpropane, N-methylpyrrolidone, and the two isocyanates werestirred at 70° C. into the mixture of polyester and components II andIV, which had been dehydrated at 100° C. The mixture was allowed toreact at 80° C. until the NCO value was constant. After cooling to 75°C., the acetone azine was stirred into the isocyanate prepolymer melt.The water was then introduced with vigorous stirring and the resultantdispersion continued to be stirred for a further 3 hours. Thepolyurethane dispersion was adjusted to a spread coating viscosity (8000mPa.s/25° C.) with a polyacrylic acid thickener at pH 8 as in Example 1.The film weighing 56 g/m² thus produced had a water vapor permeabilityof 13,800 g/m² d.

The comparison film obtained from a polyurethane dispersion analogous tothat of Example 5 but with the diol 11 content replaced by the equimolarquantity of hexanediol polyadipate had a water vapor permeability ofonly 400 g/m² in a film weighing 52 g/m². The solid substance (1040 g)contained 19.2 meq SO₃ Na/100 g and 0% by weight EOX in the main chain.

Transfer coating:

The dispersions described in Examples 2 and 5 were applied to acommercial separating paper (Transcote® VEM CIS of S. D. Warren Company)in a ratio by weight of 1:1 together with a polyacrylic acid thickener,using a roller coating device with coating knife cut in, to produce afilm which weighed 25 g/m² after drying at 80° to 150° C.

    ______________________________________                                        Spread coating paste:                                                         ______________________________________                                        50 parts                                                                              40% polyurethane dispersion of Example 2                              50 parts                                                                              40% polyurethane dispersion of Example 5                              1 part  polyacrylic acid thickener                                            5 parts aqueous pigment preparation adjusted to pH 8 with                             ammonia                                                               ______________________________________                                    

A spread coating paste prepared analogously from the polyurethanedispersion of Example 2 (without pigment preparation) was applied asbonding layer to the dried film. After lamination with a cotton fabricweighing about 140 g/m² and drying of the whole arrangement of layers at80° to 140° C., the water vapor permeable article obtained had a totalweight of 200 g/m² with the coatings (top coat and bonding coat)weighing 60 g/m².

The article, which was soft and pleasant to handle, had a permeabilityto water vapor of 10,600 g/m² d and a water resistance of 2000 mm.

When the amount of coating was varied from 50 g/m² to 75 g/m², thepermeabilities to water vapor were equally high with water resistancevalues of 2000 mm.

A transfer article produced from the comparison dispersions described inExamples 2 and 5 but without diol I or diol II and analogous instructure had a water vapor permeability of 1750 g/m² in a coatingweighing 60 g/m².

A further increase in permeability to water vapor can be obtained byusing a foamed bonding coat instead of the compact bonding coat ofExample 2.

A spread coating foam paste was applied to the dried film of top coat inlayers of 40 to 50 g/m².

    ______________________________________                                        Foam spread coating paste (mechanical foaming):                               ______________________________________                                        100 parts 40% polyurethane dispersion of Example 2                            2.0 parts STOKAL ® SR foamant (Stockhausen)                               0.8 parts STOKAL ® STA foam stabilizer (Stockhausen)                      1.5 part  MIROX ® AM thickener (Stockhausen)                              X parts   ammonia to adjust to pH 8-9                                         ______________________________________                                    

Weight per liter: about 500 g/l

After lamination with a cotton fabric weighing about 140 g/m² and dryingof the arrangement of coatings at 80° to 140° C., the water vaporpermeable article obtained had a total weight of 220 g/m² and the layercomposed of top coat and foamed bonding coat weighed 80 g/m².

The soft article, which had a very pleasant handle, had a water-vaporpermeability of 13,500 g/m² d and a water resistance of 2000 mm.

When subjected to discrete water droplets, the coatings were absolutelyresistant to drops and exhibited hardly any swelling in water.

Example 6

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        258.0 g                                                                              polyadipate of 1,6-hexanediol/neopentyl glycol (molar ratio                   65:35), OH number 66, molecular weight 1700                            69.2 g diol II                                                                60.0 g hexane-1,6-diisocyanate                                                2.4 g  ethylenediamine                                                        10.0 g diaminosulfonate V                                                     70.0 g acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g of solid substance contained 13.1 meq/100 g and 11.2% by weightEOX in the main chain.

Method:

A 40% dispersion was prepared by the acetone process analogously toExample 2. The permeability to water vapor of a film weighing 63 g/m²was 4400 g/m² d.

A film obtained from a dispersion in which the diol II content had beenreplaced by the equimolar quantity of a polyadipate of1,6-hexanediol/neopentyl glycol had a water vapor permeability of 800g/m² d (weight of film 54 g/m²). The solid substance (417 g) contained12.6 meq/100 g and 0% by weight EOX in the main chain.

Example 7

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        239.0 g    diol I                                                             14.7 g     EOX polyether III                                                  17.4 g     diol sulfonate IV                                                  111.5 g    dicyclohexylmethane-4,4'-diisocyanate                              17.4 g     acetone azine                                                      600.0 g    deionized water                                                    ______________________________________                                    

388 g of solid substance contained 10.6 meq SO₃ Na/100 g and 30.2% byweight EOX in the main chain.

Method:

A 40% dispersion was prepared by the acetone azine process analogouslyto Example 5.

A film weighing 56 g/m² had a WVP value of 6900 g/m².

A film obtained from a polyurethane dispersion containing, instead ofdiol I, the equimolar quantity of a polyadipate of1,6-hexanediol/neopentyl glycol (molar ratio 65:35), molecular weight2000, and otherwise having the same composition had a water vaporpermeability of only 1200 g/m² d in a film weighing 60 g/m². The solidsubstance (388 g) contained 10.6 meq SO₃ Na/100 g and 0% EOX in the mainchain.

Example 8

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        260.6 g                                                                              diethylene glycol polyadipate, OH number 45, molecular                        weight 2500                                                            66.7 g dihydroxypolypropylene glycol, OH number 56, molecular                        weight 2000                                                            11.3 g EOX polyether III                                                      3.6 g  dimethylolpropionic acid                                               50.4 g hexane-1,6-diisocyanate                                                2.0 g  ethylenediamine                                                        1.3 g  hydrazine hydrate                                                      4.1 g  diaminosulfonate V                                                     700.0 g                                                                              acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g of solid substance contained 5.4 meq SO₃ Na/100 g and 26% byweight EOX in the main chain.

Method:

A 40% dispersion was prepared by the acetone process analogously toExample 2.

A film prepared from the dispersion which had been thickened as inExample 1 had a water vapor permeability of 3600 g/m² d in a filmweighing 56 g/m².

When the diethylene glycol polyadipate in this Example was replaced bythe equimolar quantity of 1,6-hexanediol polycarbonate (molecular weight2000), the film produced from this dispersion, weighing 58 g/m², had apermeability to water vapor of 900 g/m² d. The solid substance (348 g)contained 6.2 meq SO₃ Na/100 g and 0% EOX in the main chain.

Example 9

Preparation of an aliphatic polyurethane dispersion.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        131.4 g                                                                              1,6-hexanediol polycarbonate, OH number 56, molecular                         weight 2000                                                            116.8 g                                                                              polycarbonate from triethylene glycol, OH number 56,                          molecular weight 2000                                                  19.7 g EOX polyether III                                                      6.2 g  dimethylolpropionic acid                                               10.5 g 1,4-butanediol                                                         44.2 g hexane-1,6-diisocyanate                                                58.3 g isophorone diisocyanate                                                3.5 g  ethylenediamine                                                        2.2 g  hydrazine hydrate                                                      7.2 g  diaminosulfonate V                                                     750.0 g                                                                              acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g of solid substance contained 9.5 meq SO₃ Na/100 g and 22% byweight EOX in the main chain.

Method:

A 40% dispersion was prepared analogously to Example 2 by the acetoneprocess.

A film produced from a dispersion which had been thickened as in Example1 and weighed 54 g/m² had a permeability to water vapor of 10,500 g/m²d.

When the polycarbonate of triethylene glycol was replaced by theequimolar quantity of the polycarbonate of 1,6-hexanediol, the filmobtained from this dispersion had a water vapor permeability of 1500g/m² d when the weight was 48 g/m². The solid substance (400 g)contained 9.5 meq SO₃ Na/100 g and 0% EOX in the main chain.

Example 10

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        60.9 g polycarbonate of 1,6-hexanediol, OH number 56, molecular                      weight 2000                                                            207.1 g                                                                              diol I                                                                 6.5 g  dimethylolpropionic acid                                               11.0 g 1,4-butanediol                                                         43.5 g hexane-1,6-diisocyanate                                                57.5 g isophorone diisocyanate                                                3.7 g  ethylenediamine                                                        3.3 g  hydrazine hydrate                                                      7.5 g  diaminosulfonate V                                                     700.0 g                                                                              acetone                                                                600.0 g                                                                              water                                                                  ______________________________________                                    

400 g of solid substance contained 9.9 meq SO₃ Na/100 g and 25.4% byweight EOX in the main chain.

Method:

A 40% polyurethane dispersion was prepared from these components by theacetone process as in Example 2.

To determine the permeability to water vapor, a film weighing 52 g/m²was prepared from the dispersion after it had been thickened with 3.0 gof a 30% solution of poly-N-vinylpyrrolidone. The water vaporpermeability was 12,300 g/m² d.

A comparison film produced from a polyurethane dispersion analogously toExample 10 without containing diol I but containing the equimolarquantity of the polycarbonate of hexanediol and having otherwise theidentical composition had a water vapor permeability of 1500 g/m² d in afilm weighing 48 g/m².

Transfer coating:

The polyurethane dispersion which had been thickened withpoly-N-vinylpyrrolidone as above was used for producing a top coat afterit had been pigmented as in Example 2. The spread coating pastedescribed in Example 2 was used as bonding coat. The textile substrateused was a mixed fabric of cotton/polyester weighing 100 g/m². Thecoating composed of top coat and bonding coat weighed 53 g/m². The watervapor permeability was 11,100 g/m² d. When the bonding coat paste wasused as a so-called beaten foam dispersion with a unit weight of 500g/l, the water vapor permeability of the whole coating weighing 55 g/m²was 14,500 g/m² d.

The coatings from all the Examples according to the invention wereresistant to drops and showed hardly any swelling in water.

When the comparison dispersion mentioned in Example 10 was used as topcoat and the comparison dispersion mentioned in Example 2 was used asbonding coat, the water vapor permeability values were 800 g/m² d(compact) and 950 g/m² d (foamed).

Example 11

Preparation of an aliphatic polyurethane dispersion for water vaporpermeable layers.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        213.8 g                                                                              tetraethylene glycol phthalic acid polyester, OH number 56,                   molecular weight 2000, EOX content 54%                                 150.0 g                                                                              1,6-hexanediol phthalic acid polyester, OH number 56,                         molecular weight 2000                                                  17.0 g polyether prepared by propoxylation of trimethylolpropane,                    OH number 385, molecular weight 435                                    65.1 g hexane-1,6-diisocyanate                                                11.1 g isophorone diisocyanate                                                1.5 g  ethylenediamine                                                        16.6 g diaminosulfonate V                                                     650.0 g                                                                              acetone                                                                710.0 g                                                                              water                                                                  ______________________________________                                    

475 g of solid substance contained 17.8 meq SO₃ Na/100 g and 24% byweight EOX in the main chain.

Method:

The two phthalic acid polyesters were dehydrated together with thepolyether in an aspirator vacuum at 100° C. After the mixture was cooledto 65° C., the hexane-1,6-diisocyanate and isophorone diisocyanate wereadded. After the exothermic reaction has subsided, the mixture wasstirred for 5 hours at 80° C. until an NCO value of 3.3±0.1% wasreached. The mixture was cooled to 65° C. and dissolved in acetone. Amixture of ethylenediamine, diaminosulfonate V, and 210 g of water wasadded to the acetone solution at 50° C. over a period of about 15minutes. Immediately thereafter a further 500 g of water was added overa period of 5 minutes to form a dispersion. The acetone was distilledoff until an acetone content of less than 1.0% was reached. Theresultant dispersion was adjusted with water to a solids content of40.0%.

To determine the permeability to water vapor, a film weighing 75 g/m²was prepared after thickening the dispersion as in Example 1. The watervapor permeability was 23,700 g/m² d.

A comparison film prepared from a polyurethane dispersion which insteadof containing the hydrophilic tetraethylene glycol phthalic acid estercontained a larger quantity, corresponding to the molar quantity, of1,6-hexanediol phthalic acid ester but which otherwise had the samecomposition had a water vapor permeability of only 200 g/m² d in a filmweighing 54 g/m². The solid substance contained 17.8 meq SO₃ Na/100 gand 0% EOX in the main chain.

Direct coating:

The dispersion thickened as in Example 1 was applied to polyestertaffeta having a fabric weight of about 60 g/m² by the direct processusing an air doctor blade and the coating was dried at 80° to 150° C.The dispersion was applied a second time and also dried to form acoating weighing about 20 g/m².

    ______________________________________                                        Spread coating paste:                                                         ______________________________________                                        100 parts   40% polyurethane dispersion                                       1 part      25% ammonia (adjusted to pH 8-9)                                  1 part      polyacrylic acid thickener                                        ______________________________________                                    

The spread coating paste described in Example 5 (polyurethanedispersions of Examples 2 and 5) was applied as a finish in a singlecoating by the direct process using an air doctor blade. After drying at80° to 150° C., the total coating weight was about 25 g/m². The watervapor permeable article, which was pleasant to handle, had a water vaporpermeability of 5100 g/m 2d and a water resistance of 2000 mm.

Example 12

Preparation of a polyurethane dispersion using a polyether diol tointroduce the EOX units into the main chain.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        237.5 g                                                                              polycarbonate of 1,6-hexanediol, OH number 56, molecular                      weight 2000                                                            72.5 g polyether diol of ethylene oxide and propylene oxide (weight                  ratio of 1:1), OH number 56, molecular weight 2000                     105 g  polyether diol of propylene glycol, OH number 56, molecular                   weight 2000                                                            6.4 g  dimethylolpropionic acid                                               75.6 g hexane-1,6-diisocyanate                                                2.85 g ethylenediamine                                                        1.75 g hydrazine hydrate                                                      7.12 g diaminosulfonate V                                                     825.0 g                                                                              acetone                                                                1300.0 g                                                                             water                                                                  ______________________________________                                    

508.1 g of solid substance contained 7.4 meq SO₃ Na/100 g and 7.1% byweight EOX in the main chain.

Method:

The polycarbonate and the two polyether diols were dehydrated undervacuum at 100° C. Dimethylolpropionic acid was added at 100° C. andhexanediisocyanate was added at 80° C. After 3 hours at 100° C., theresultant prepolymer was dissolved in acetone. The mixture of chainlengthening agents comprising ethylenediamine, hydrazine hydrate, anddiaminosulfonate V dissolved in 120 g of water was added at 50° C. Theremaining quantity (627 g) of water was then stirred in. After continuedstirring for 21/2 hours at 40° C., the acetone was removed bydistillation. A stable 28% dispersion was obtained. The polyurethanedispersion was thickened as in Example 1. The film weighing 72 g/m² thusproduced had a water vapor permeability of 8,800 g/m² d.

Example 13

Preparation of a polyurethane dispersion using a polyether diol tointroduce the EOX units into the main chain.

    ______________________________________                                        Formulation:                                                                  ______________________________________                                        191.5 g                                                                              polyadipate of 1,6-hexanediol, OH number 133, molecular                       weight 840                                                             60.0 g polyether diol of ethylene oxide and propylene oxide (weight                  ratio of 1:1), OH number 56, molecular weight 2000                     22.5 g diol sulfonate IV                                                      8.0 g  trimethylolpropane                                                     34.7 g N-methylpyrrolidone                                                    146.7 g                                                                              dicyclohexylmethane-4,4'-diisocyanate                                  26.9 g hexane-1,6-diisocyanate                                                25.1 g acetone azine                                                          802.0 g                                                                              deionized water                                                        ______________________________________                                    

462.9 g of solid substance contained 11.4 meq SO₃ Na/100 g and 6.5% byweight EOX in the main chain.

Method:

A mixture of the polyester, the polyether, and the diol sulfonate weredehydrated under vacuum at 100C, after which was addedtrimethylolpropane, N-methylpyrrolidone, and the two isocyanates withstirring at 70° C. The mixture was allowed to react at 90° C. until theNCO value was constant. After cooling to 75° C., the acetone azine wasstirred into the isocyanate prepolymer melt. The water was thenintroduced with vigorous stirring and the resultant dispersion wasstirred for a further 3 hours. The solids content was 35%. Thepolyurethane dispersion was thickened as in Example 1. The film weighing62 g/m² thus produced had a water vapor permeability of 10,800 g/m² d.

Example 14

(comparison according to U.S. Pat. No. 4,108,814)

A polyurethane dispersion was prepared according the Example 1 of U.S.Pat. No. 4,108,814 using the following components:

    ______________________________________                                        340 g   polyadipate of 1,6-hexanediol and neopentyl glycol, OH                        number 66, molecular weight 1700                                      12.8 g  diol sulfonate IV                                                     69.6 g  hexane-1,6-diisocyanate                                               33.8 g  diaminosulfonate V (45% aqueous solution)                             700.0 g deionized water                                                       ______________________________________                                    

437.6 g of solid substance contained 25.1 meq SO₃ Na/100 g and 0% byweight EOX in the main chain.

To determine the permeability to water vapor, a film weighing 65 g/m²was prepared after thickening the dispersion as in Example 1. The watervapor permeability was 2200 g/m² d.

What is claimed is:
 1. A coating composition used for the preparation ofcoatings having a water vapor permeability of at least 2500 g/m² per dayusing the DS 2109 TM1 method comprising(A) a polyurethane containing (1)from 0.1 to 75 meq per 100 g of polyurethane (A) of ionic groups and (2)11 to 50% by weight, based on polyurethane (A), of polyethylene oxide--(CH₂ CH₂ O)_(n) -- units having a sequence length n of from 2 to 25incorporated into the main chain, wherein said polyurethane (A) isprepared from reactive components comprising(I) one or morepolyisocyanates, (II) one or more polyols having a number averagemolecular weight of from 350 to 5000, with the proviso that if any suchpolyol is a sulfonated polyether diol having the formula ##STR6##wherein R denotes hydrogen or an organic group having 1 to 8 carbonatoms, m and n independently represent the numbers 1 to 10, p representsthe numbers 0, 1, or 2, and M denotes ammonium or the cation of analkali metal, then at least one additional polyether polyol containingethoxy groups must also be present, and (III) one or more chainlengthening agents having a molecular weight of from 32 to 349; and (B)from 30 to 80% by weight, based on the sum of components (A) and (B), ofan aqueous phase.
 2. A coating composition according to claim 1 used forthe preparation of coatings having a water vapor permeability of atleast 2500 g/m² per day using the DS 2109 TM1 method comprising(A) apolyurethane containing (1) from 0.1 to 75 meq per 100 g of polyurethane(A) of ionic groups selected from the group consisting of (a) alkalimetal and ammonium salts of carboxylate groups, (b) alkali metal andammonium salts of sulfonate groups, (c) ammonium groups, and (d)mixtures thereof, and (2) 11 to 50% by weight, based on polyurethane(A), of polyethylene oxide --(CH₂ CH₂ O)_(n) -- units having a sequencelength n of from 2 to 25 incorporated into the main chain, wherein saidpolyurethane (A) is prepared from reactive components comprising(I) oneor more polyisocyanates, (II) one or more polyols having a numberaverage molecular weight of from 350 to 5000, with the proviso that ifany such polyol is a sulfonated polyether diol having the formula##STR7## wherein R denotes hydrogen or an organic group having 1 to 8carbon atoms, m and n independently represent the numbers 1 to 10, prepresents 0, 1, or 2, and M denotes ammonium or the cation of an alkalimetal, then at least one additional polyether polyol containing ethoxygroups must also be present, and (III) one or more chain lengtheningagents having a molecular weight of from 32 to 349; and (B) from 30 to80% by weight, based on the sum of components (A) and (B), of an aqueousphase.
 3. A coating composition according to claim 1 wherein component(II) comprises(a) at least one polyol corresponding to the formula##STR8## wherein R denotes hydrogen or an organic group having 1 to 8carbon atoms,m and n independently represent the numbers 1 to 10, and Mdenotes ammonium or the cation of an alkali metal, and (b) at least oneadditional polyether polyol containing ethoxy groups present inquantities such that at least 25% of the ethoxy groups incorporated intothe main chain of polyurethane (A) are derived from said additionalpolyol.
 4. A coating composition according to claim 1 used for thepreparation of coatings having a water vapor permeability of from 2500to 25,000 g/m² per day using the DS 2109 TM1 method.
 5. A coatingcomposition according to claim 1 wherein polyurethane (A) contains from14 to 40% by weight, based on polyurethane (A), of polyethylene oxideunits incorporated into the main chain.
 6. A coating compositionaccording to claim 1 wherein polyurethane (A) contains ionic groups in aquantity of from 0.5 to 40 meq per 100 g of polyurethane (A).
 7. Acoating composition according to claim 1 wherein polyurethane (A)contains from 11 to 35% by weight, based on polyurethane (A), ofpolyethylene oxide units incorporated into the main chain.
 8. A coatingcomposition according to claim 1 wherein the sequence length n of thepolyethylene oxide --(CH₂ CH₂ O)_(n) -- units is from 3 to
 12. 9. Acoating composition according to claim 1 wherein at least one polyol ofcomponent (II) corresponds to the formula ##STR9## wherein R denoteshydrogen or an organic group having 1 to 8 carbon atoms,m and nindependently represent the numbers 1 to 10, and M denotes ammonium orthe cation of an alkali metal, andat least one additional polyetherpolyol containing ethoxy groups is present.